1. Field of the Invention
This invention relates to a wireless communications system having a communications apparatus, which accommodates a communication line, and a wireless communications apparatus wirelessly connected to this apparatus, and to a method of controlling this communications system.
2. Description of the Related Art
In the prior art notification of an incoming call arriving at an analog trunk is given by causing the intermittence of an incoming call signal having a certain fixed frequency. (The frequency used most widely in Japan in 16 Hz, while that used in the United States is 20 Hz). A telephone connected to the analog trunk causes an incoming call bell to ring when the incoming call signal is being sent to the telephone from the analog trunk. When the incoming call signal stops arriving from the analog trunk, the telephone halts the ringing of the bell. In other words, the telephone connected to the analog trunk causes a pattern representing the intermittence of the incoming call signal sent from the analog trunk to be reflected as is in the way the incoming call bell is rung.
Telephone exchanges include those of the type which change the intermittence of the incoming call signal depending upon the type of originator. FIG. 22 illustrates an example of a pattern representing the intermittence of an incoming call signal in a telephone exchange of this kind. According to Pattern 1, the incoming call signal continues for one second and is halted for two seconds. According to Pattern 2, continuation of the incoming call signal for 250 milliseconds and halting of the incoming call signal for 250 milliseconds is repeated twice, after which the incoming call signal is halted for two seconds. According to Pattern 3, continuation of the incoming call signal for 250 milliseconds and halting of the incoming call signal for 250 milliseconds is repeated three times, after which the incoming call signal is halted for 1.5 seconds. When an incoming call signal arrives at a telephone connected to an extension in a certain private branch exchange (PBX), for example, Pattern 1 is used for an incoming call signal from an outside line, Pattern 2 for an incoming call signal from an extension and Pattern 3 for an incoming call signal that has been transferred from an outside line. The user of the telephone connected to this extension of the private branch exchange can recognize the type of originator by the difference in the ringing of the incoming call bell.
A cordless telephone comprises a master set and a slave set. When an incoming call signal from an analog trunk is detected by the master set, the master set transmits a control signal which notifies the slave set of the incoming call. Upon receiving this control signal giving notification of the incoming call, the slave set causes the incoming call bell to ring according to a single pattern, regardless of whether the call is from an extension or outside line or is a transferred call, until a control signal halting the ringing of the bell arrives from the master set or until the slave set is taken off the hook.
The specification of Japanese Patent Application Laid-Open No. 3-114340 discloses an arrangement in which the master set discriminates whether an incoming call is from an extension or outside line and changes the tone (the frequency) of the ringing bell at the slave set accordingly.
The specification of Japanese Patent Application Laid-Open No. 5-55999 discloses an arrangement in which an incoming call tone from a telephone line or an incoming call tone produced by a master set is transmitted to the slave set by a speech channel and a ringing tone is produced by speaker at the slave set.
However, in the prior-art cordless telephone comprising master and slave sets as set forth above, the slave set, upon receiving the control signal giving notification of the incoming call, causes the incoming call bell to ring according to the same pattern regardless of whether the call is from an extension or outside line. As a consequence, the intermittence of the incoming call signal from the analog trunk cannot be reflected in the way the incoming call bell of the slave set is rung, thus making it impossible for the user to determined the type of originator (extension, outside line, transfer, etc.) from the difference in the ringing pattern of the bell.
Further, the wireless communications apparatus of the kind described in Japanese Patent Application Laid-Open No. 3-114340 requires a sound source for each different type of tone, resulting in an apparatus of increased size.
Further, the wireless communications apparatus of the kind described in Japanese Patent Application Laid-Open No. 5-55999 is such that the incoming call tone passes through a wireless link. This results in an incoming call tone of poor quality.